Not sure I understand what arrow weight has to do with ethics...

If you are shooting an arrow heavy enough for your bow to handle without it blowing up on you...it is gonna be fine to shoot a deer with. Not to say you can't mess with some weights to maximize your setup for the best combo of speed and KE, but, when talking about deer...they are not hard to shoot thru. If in doubt, lean towards the heavier side. I never choose my setup with any KE in mind...the resulting KE is what it is and I know it will be fine. If/when I go to africa or after moose, then I will make sure my chosen setup is producing the needed KE. The 85 and 90 ft/lbs you mentioned is no where near target KE...those #'s are very high.

When it comes to broadheads, IMO, leaning towards the heavy side is always going to benefit you.A higher FOC is going to provide you a more stable arrow flight and thus, an easier time getting good broadhead flight.